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Younan Xia

Bio: Younan Xia is an academic researcher from The Wallace H. Coulter Department of Biomedical Engineering. The author has contributed to research in topics: Nanocages & Nanowire. The author has an hindex of 216, co-authored 943 publications receiving 175757 citations. Previous affiliations of Younan Xia include Washington University in St. Louis & University of Texas at Dallas.


Papers
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TL;DR: In this article, a replacement reaction between the surface of a nanoscale template and the solution of an appropriate salt precursor is used to synthesize metal nanostructures with well-defined hollow interiors.
Abstract: We have recently developed a simple and versatile route to the large-scale synthesis of metal nanostructures with well-defined hollow interiors. The key step of this process involves a replacement reaction between the surface of a nanoscale template and the solution of an appropriate salt precursor. The capability and feasibility of this method have been demonstrated by preparing hollow nanostructures of gold with a range of different morphologies (e.g., triangular rings, prism-shaped boxes, cubic boxes, spherical capsules, and tubes). In addition to gold, this method also worked well for other metals such as platinum and palladium (see Figure for an SEM image of Pd nanotubes). These metal nanostructures with hollow interiors are useful as fillers for generation of ultralight composites; they are also interesting for new types of applications that include use as components for highly sensitive colorimetric sensors and as effective, recoverable catalysts.

947 citations

Journal ArticleDOI
TL;DR: In this paper, a general approach that generates nanoscale hollow structures of metals by reacting solutions of appropriate salt solutions with solid templates of a more reactive metal is described, which are completely converted into soluble species during the replacement reaction.
Abstract: This paper describes a general approach that generates nanoscale hollow structures of metals by reacting solutions of appropriate salt solutions with solid templates of a more reactive metal. Typical examples include Au3+, Pt2+, and Pd2+ salts and nanoparticles or nanowires of silver. The morphology, void space, and wall thickness of these hollow structures are all determined by the solid templates, which are completely converted into soluble species during the replacement reaction. Both electron microscopy and diffraction studies indicate that single crystalline hollow structures of metals can also be obtained when the templates are single crystals. These metallic hollow structures, having well-controlled sizes and shapes, are expected to find use in a number of applications that involve nanoscale encapsulation, drug delivery, plasmon photonics, and calorimetric sensing.

882 citations

Journal ArticleDOI
TL;DR: A comprehensive review of superparamagnetic colloid research can be found in this article, with a focus on those systems that can be prepared as monodisperse samples and in relatively large quantities.
Abstract: The aim of this article is to provide a comprehensive review of current research activities that center on superparamagnetic colloids. We begin with an overview of synthetic strategies that have been developed for generating both nanoscale and mesoscale superparamagnetic colloids, with a focus on those systems that can be prepared as monodisperse samples and in relatively large quantities. We then discuss a variety of techniques that have been exploited for modifying surface properties, as well as for controlling the assembly and patterning of these magnetically active colloids. Towards the end, we highlight a range of innovative applications enabled by the unique combination of superparamagnetism and colloidal suspension. We conclude this review article with personal remarks and perspectives on the directions toward which future research in this area might be directed.

880 citations

Journal ArticleDOI
TL;DR: A strategy that combines physical templating and capillary forces to assemble monodispersed spherical colloids into uniform aggregates with well-controlled sizes, shapes, and structures that can serve as a useful model system to investigate the hydrodynamic and optical scattering properties of colloidal particles having nonspherical morphologies.
Abstract: This paper describes a strategy that combines physical templating and capillary forces to assemble monodispersed spherical colloids into uniform aggregates with well-controlled sizes, shapes, and structures. When an aqueous dispersion of colloidal particles was allowed to dewet from a solid surface that had been patterned with appropriate relief structures, the particles were trapped by the recessed regions and assembled into aggregates whose structures were determined by the geometric confinement provided by the templates. We have demonstrated the capability and feasibility of this approach by assembling polystyrene beads and silica colloids (> or =150 nm in diameter) into complex aggregates that include polygonal or polyhedral clusters, linear or zigzag chains, and circular rings. We have also been able to generate hybrid aggregates in the shape of HF or H2O molecules that are composed of polymer beads having different diameters, polymer beads labeled with different organic dyes, and a combination of polymeric and inorganic beads. These colloidal aggregates can serve as a useful model system to investigate the hydrodynamic and optical scattering properties of colloidal particles having nonspherical morphologies. They should also find use as the building blocks to generate hierarchically self-assembled systems that may exhibit interesting properties highly valuable to areas ranging from photonics to condensed matter physics.

848 citations


Cited by
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: A review of gold nanoparticles can be found in this article, where the most stable metal nanoparticles, called gold colloids (AuNPs), have been used for catalysis and biology applications.
Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

11,752 citations